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c. 'r. HOFFMAN Re. 20,245 MEANS FOR AUTOMATICALLY DEFROSTING RBFRIGERATING' UNITS Original Filed Sept. 21, 1929 'T Sheets-Sheet 1 Jwoemtoz Jan. 12, 1937. c. T. HOFFMAN mums FOR AU'IDMATICALLY DEFROSTING REFRIGERATING mums Original Filed Sept. 21, 1929 7 Sheets-Sheet 2 caoLnvs cimmasn Jan. 12, 1937. c. T. HOFFMAN R 0. 4 v MEANS FOR AUTOMATICALLY DEFROSTING REFRIGERATIHG UNITS v Original Filed Sept. 21, 19:29 7 Sheets-Sheet 5 %I60 1 A v v Q 8 =a f I g Jan. 12, 1937. c. 'r. HOFFMAN R 20,245

MEANS FOR AUTOMATICALLY DEFROSTING REFRIGERATING UNITS Original Filed Sept. 21, 1929 7 Sheets-Sheet 4.

. Jam I Jan. 12, 1937.

C. T. HOFFMAN MEANS FOR AUTOMATICALLY DEFROSTING REFRIGERATING UNITS Original Filgd Sept. 21, 1929 7 Sheets-Sheet 5 r0 110 l. CURRENT sum,

- Jwuentw m RECTIFIER 4- Jan. 1 2, 1937. c. T. HOFFMAN R e. 20,245

mums FOR-AUTOMATICALLY DEFROSTING REFRIGER TING pun-s Origing}. Filed Sept. 21, 1929 sheets-$heet 6 Jan. 12, 1937. I c T, HOFFMAN RE- 20,245

MEANS FOR AUTOMATICALLY DEFROSTING REFRIGERATING UNITS Original Filed Sept. 21, 1929 '7 Sheets-Sheet 'T saws Fan MAINTAIN/Ara m: EVA PORflTDR WITHIN PRIDITERMINZD TIMPERATURE Lnvlrra up 001.0 g wn-Roth conmezaeon L Gil mama Jan. 2, 1931 UNITED T T nus; 'ms ronaurom'ncmrnsmosmc- I nsrmcmrmo-umrs; Charles '1'. num'wemingian, n. 0.. bydirect andmesnealcignm'cntpto'liloyd m' .xeiu nsmoms I Original m. 1,886,953, dated November-8, 1532.

Serial No. 394,209, September 21, 1929.

Apn i- I cation for reissue January 25, 1933, Serial No. I

' 46 Claim.

This lnventionrelates to refrigeration, and has n particular reference to the carrying forward of the fundamental featuresand principles set forth in my copending application, Serial No. 375,647,

'filed July 3, 1929, directed to means for automatically defrosting the refrigerating unit at predetermined intervals.

A primary object 01' the invention is to provide a novel construction and arrangement of parts to adapt the mechanism of my aforesaid application to an icebox .of the household type wherein the refrigerating coil is supported in the box and spaced from the walls thereof. In that connection the invention contemplates the provision of means for positioning the ice contacting and following member within the box in close proximity to the ice forming surface while the mechanism actuated and controlled by the circuit controller of said member is concealed in a wall of the box.

Another object of the invention is to provide means for preventing the premature functioning of the defrosting apparatus in ice boxes using a so-called "cold control" which permits the user of the box to materially reduce the temperature in the refrigerating unit for the purpose of freez-.

ing liquids other than water, such for example, as ice cream. While the present defrosting means is intended to operate by contact with the ice, nevertheless, since the circuit controller is primarily a thermostat element intended to be actuated at 32 F. or lower by contact with the ice, it

control thermostat is located, to assure that the pilot thermostat will open or break the circuit of the low temperature contact of themain circuit controller when demanded while unusual cold conditions exist in the box. Thus, the present invention provides fully for taking care of all conditions of box operation and insures the operation and control of the circuit to the motor by the formation of ice on the refrigerating unit (the ice being the factor that it is desired to eliminate) to secure proper low temperature within'the boxwith a minimum consumption of electrical energy for driving the motor, etc,

it might not be desired to use current of low voltage.

the line 4-1 of Figure 3.

A further object of-the invention is to provide means whcreby"110 volt A. C. may be used to actute the control arm and switch means when a With the above'and other objects in view, the

invention consists inthe novel features of con- ,struction, combination and 'arrangement'of parts as will be hereinafter more fully described, illusinthe appended claims.

A preferred andpractical embodiment of the invention is shown inthe acconipanying drawinES in which:

trated in the accompanying drawings and'deilned Figure 1 is a sectional view of one corner of taken on Figure 5 is a vertical'cross sectional view taken on the line 5-5, Figure "3.

Figure 6 is a detail elevation of the top of an ice box showing the defrosting panel including the manual setting control and the visual indicator.

Figure 7 is a detail diagrammatic view illustrating the circuits involved.

Figure 8 is a detail view illustrating a solenoid for using 110 volt A. C. current which may be substituted forthe elect'romagnets of Figure '7 whiieh preferably use rectified low voltage cur ren a rectified direct Figure 9 is a wiringdiagram of the two circuit controllers. v

I Figure 10 is a detail view illustrating a modification of the invention which utilizes a secondary or pilot thermostat-switch which operates automatically at temperatures below freezing. I

Figure 11 is an enlarged vertical cross sectional view of the coldcontrol thermostat-switch. Figure 12 is a vertical sectionalview taken on the line |2l2 of Figure .11. :I 1.

Figure 13 is a detail view of the collarelement for causing positive' movement of the coldcontrol thermostat switch arm in one direction andyielding movement in the fother direction.

Figure 14 is a diagrammatic view illustrating the application of the invention to a refrigerator.

Similar reference characters designate corresponding parts throughout the several figures of the drawings.

The present defrosting means is intended tobe used on automatic refrigerators, such, for example, as the type including a cabinet having a cooling chamberfor enclosing or housing the evaporator or refrigerating unit, the said refrigerating unit being suitably connected with means for circulating a refrigerant through the same. together with means for maintaining the evaporator or refrigerating unit within predetermined temperature limits. That is to say, the present invention contemplates the provision of defrost-.

ing means operating in conjunction with the instrumentalities referred to but in addition to the usual thermal or pressure control switch means for maintaining the evaporator or cooling unit within predetermined temperature limits which maintains the usual refrigerating cycle. Therefore, it will be apparent that the present construction and arrangement may be readily applied toor embodied in refrigerators having the essential elements pointed out and is intended to automatically control or modify the usual refrigerating cycle to the extent that it will suspend such cycle ior a sufllcient period to effect defrosting and then automatically restore the cycle to its usual automatic controls.

Referring to the drawings, it will be observed from Figure 1 that the ice contacting and following member A may be arranged in the cooling compartment of the ice box, between a coil or coil baille I of the refrigerating unit and the rear wall 2 of the box so that as the ice builds out on the baffle or coil as the case may be, it will contact with the member A to cause the thermostat switch therein to operate. This member A is carried by the control arm B which projects through an opening a in the top wall 3 (Fig. 2) of the box. This opening may be closed by a liquid seal device which consists of a cup 4 carried by the arm and a ferrule member 5 depending through the opening a.

The arm B according to the present arrangement includes the parts B, B2 and B3 the latter being pivoted as at C on the adjustable base D. The part B3 is provided with an enlargement or platform portion B4 on which are suitably mounted the sliding dogs 0 and 0'. 0n the pivot C is also mounted the switch arm F, and the said switch arm and the element B3 of the control arm are connected by the spring G. The dogs 0 and 0' are adapted to be alternately engaged by the sliding plunger P connected with the spring armature element N of an electromagnet device M. When the circuit is closed to the magnets M the plunger P will be moved to engage the dogs 0 and O" and cause the relative position of the arms B3 and F to change, that is change from the position shown in Figure 1 to the position shown in Figure 3 except as determined by the tension of spring 32, the purpose of which, primarily, is to render effective its action regardless of the position of the manual control.

In the position of parts shown in Figure 1 the apparatus is set so that when the ice formation.

builds up on the coil or coil baffle and touches the member A, the thermostat switch therein will temporarily close the circuit to the magnet M and cause the head of the plunger P to actuate the dog 0 and cause it to engage the switch lever or arm F at one side of its center and move it against the tension of the spring G which will cause the arm F to move away from the terminals T which are connected to the motor of the refrigerating apparatus and toward the terminals '1" which are connected to the defrosting indicator circuit which includes the defrosting indicator lamp L.

The position of parts during the defrosting period is clearly shown in Figure 3. In this figure the switch arm F is shown as against the terminals T of the defrosting circuit while the circuit which controls the motor of the refrigerating apparatus'is broken due to the fact that the switch arm has moved away. The switch arm F remains in the position shown in Figure 3 until the ice is completely melted from the entire ice forming unit and the temperature of the box has risen sufliciently to operate the thermostat switch of the member A to again close the circuit to the magnets M and cause the plunger P to engage the dog 0' and throw the arm F back to the position of Figure 1.

While the apparatus is in the position shown in Figure 3, that is, during the defrosting period it will be observed that the arm B and its supporting bracket portion B are under thetension of the spring B2 connected with the arm B3. It will thus be apparent that the tension of the spring B2 may be less than the tension of the spring G which connects the arms B3 and F. This difference in tension is only required to be sufficient to permit the complete action of the arm B3 under any setting of the manual control. That is to say, under the minimum refrigerating cycle setting, the ice contacting and following member will have a maximum movement, for instance, less than one-half of the required movement of member B3 to permit the dog 0' to engage the head of the plunger P. This difference in action is compensated for fully by the tension of spring B2. The combined tension of the springs G and B2 will cause the member A to positively contact with and follow the meltingice until it rests on the coil or coil baiiie where it remains until the end of the defrosting period.

In connection with the spring B2, it will be observed that the tension of'the same is adjustable through the medium of the adjusting screw :2.

The foregoing description describes generally the operation of the device and reference will now be made to the details of the specific parts of the apparatus.

As previously indicated the apparatus briefly described is mounted on the adjustable base D which base is provided with the slots 6 adapted to engage with the guide pins 1 carried by a permanent base 8 suitably anchored to a convenient part of the box and which may receive a cover ii for removably covering and concealing or housing the entire apparatus to meet underwriters requirements. The unit thus made, may be conveniently placed in a wall of the ice box above the cooling chamber so that the arm B projects through the hole a in a wall of the box. The entire assembly may be surrounded by insulation III of the type usually used in ice boxes of this character and may be readily accessible and removable through the cover ii on the top of the box.

The adjustable base D mounted on the permanent base 8 is preferably provided with bracket members ll for receiving a grooved nut l2 which is held between the members in such a way that a manually operated rod l3 having the screw threads I4 may be utilized to shift the base or platform D in the direction of the arrow shown in Figure 3. The platform or base D is shown as man being set in-position for the refrigerating cycle, that is inv position to permit of, for

example, a fifteen" day refrigerating cycle so that tionary base 8 and which serves to pivotally support the arm B and-its associated parts.

rod l3 so that it will turn but not movelongitudinally is to provide the same with a collar l6 which will operate in a socket i1.

I Surrounding the rod I3 is a dial l8 having thereon suitable indications, for example, the numerals "1 to "15 inclusive which may indicate the number of days of'the refrigerating cycle. This indicia is adaptedto be read in connection with a hand or pointer i9 carried by the operating knob 20 which is keyed or otherwise suitably made fast to the end of the rod l3. This knob 20 and dial l8 are located on the upper or so-called defrosting panel of the box as shown in Figure 6.

The defrosting panel is designated generally as 2| and is preferably arranged above the door 22 so that the user of the box may always conveniently and readily be able to determine from the dial 'IB when the defrosting period will take place, or on the other hand, can adjust the refrigerating cycle in such a way as to make the defrosting period occur at certain specified intervals.

In addition to the manual control and dial being located on the defrosting panel the latter alsoincludes a window 23 behind which the defrosting'lamp L of the defrosting circuit is located.- This window may be provided with suitably colored glass or may be provided with any suitableindicia such, for example, as the word Defrosting" to announce at all times to the user that the box is defrosting and that the refrigerating cycle has temporarily ceased.

Referring more particularly to the ice contacting and following member A, it will be observed that the same comprises a metallic casing which houses a thermostat switch adapted to close an electric circuit temporarily at a predetermined low temperature point and a predetermined high temperature point. In the example shown the thermostat switch includes a thermostat element 24 of any suitable type which is anchored at one end of the casing while its other end engages with a circuit closing arm 25 which may be suitfrom the source of electrical energy through the electromagnets M, arm 25 and contact 26 to the wire 26a which connects with the arcuate contact 28 which in turn isin contact with the sliding switch arm 29 which is'in electrical contact 3 with the plate 2 9a, to which the remainder or wire 26a is connected. This closing of the circuit causes the electromagnets M to operate the plunger. elementN, thereby to engage the'dog O and pull it toward the magnets for the purpose of forcing the switch arm F fromthe position shown in Figures .1 and 7 to. the position shown in Figure 3, thereby placing the ice contacting and following member A under tension and causing it to follow the ice formation until all ofthe ice has melted from the ice forming surface and the temperature rises to' cause the thermostat .element 24 to move the arm 25 back into engagement with e high temperature contact 21.

When the igh temperature contact 21 is engaged by the arm 25 the circuit will again be closed through the electromagnets and will go back to the source of energy over the wire 21a which connects with the arcuate member 28a and which. arcuate member is engagedrby the spring contact member 29 carried by the underside of the arm F and which is connected as above shown to wire 26a. When the circuit is closed through the high, temperature contact 21 the electromagnets will actuate the armature N to pull the dog 0' forward and cause the parts to move from the position shown in Figure 3 back to the position shown in Figures 1 and 'I.

When the switch arm F is in the position shown in Figures 1 and 7 the switch contacts 30 carried by the arm F are in engagement with the motor circuit contacts T of Figure 1 and 3| of Figure 7, thereby maintaining the refrigerating cycle in the usual manner. However, on the other hand, when the switch arm is in the position shown in Figure 3 the contacts 30 break the circuit to the motor and prevent the restoration of the refrigerating cycle until all of the ice is melted from the ice forming unit or evaporator. While the circuit is broken to the motor of the refrigerating apparatus, the contacts 30 are in engagement with the contacts T of Figure 1, which are the same as the contacts 3| of Figure 7 of the indicating circuit 32, which includes the lamp L or equivalent indicator.

Another important and distinctive feature of the present invention resides in the provision of means for preventing premature closing of the circuit between the arm 25 of the member A and the low temperature contact 26. When the present device is used in connection with an ice box having a so-called cold control feature or its equivalent, it has been found that the same will operate when the ice contacts with the metallic casing thereof and the low temperature contact 26 is set at ice temperature in relation .to the ice forming unit. In other words, as the ice builds out to the circuit controller, it has been observed that the arm 25 will hang around a temperature safely above the setting of the low temperature contact due to the fact that the relatively warm air in the box is continuously circulating between the ice and themember A and around member A However, when the ice builds out to and contacts with the circuitcontroller, the latter will immediately respond to ice temperature and the contacts 25 and 26 will close the circuit previously described. In, refrigerators using the socalled cold control feature which if improperly attended permits the temperature to go below freezing, thereis a possibility that the switch of the member A would prematurely operate due to the fact that the low temperature adjacent the unit would causethe arm 25 to engage with the contact 26 before the ice formation builds out to the member A. To avoid such a contingency a cold control thermostat device A2 may be employed. This device may be posi-- tioned anywhere adjacent the refrigerating unit,

but for the sake of convenience may be carried by the lower end of the arm B which carries the member A, as shown in Figure l0. This thermostat device A2 is shown in detail in l'-ig-.

43 keyed or pinned to the member 38 so that as u the temperature lowers in the box to a predetermined point above the degree at which the contact 26 is set, the thermostat element S will cause the post 36 to rotate and carry with it the collar 43 whereby the offset portion 42 will move the arm 4| so that its upper end, which carries the contact 4Ia. will be moved away from the contact 4Ib. This contact 4| b is connected with the wire 26a and likewise the metallic circuit closing arm 4| is connected with the wire a. Thus, when excessive low temperature prevails, the circuit-including the low temperature contact 26 is automatically opened or broken by this so-called cold control thermostat. When the temperature in the box is normal the thermostat element S will maintain the contacts Ma and 4Ib in engagement so that the arm 25 in engaging the contact 26 will always be ready to close the circuit when the ice builds out and touches the member A. When the temperature is sufficiently above the point at which contact 26 is set, a spring 44 on the collar 43 engages and presses the arm II in a direction to maintain its contact 4Ia against the contact 4Ib. It will, of course, be understood that when temperature at some predetermined point higher or lower than the point at which contact 26 is set prevails the offset portion 42 moves away from engagement with the arm 4| and the spring 44 exerts its force. The movement of the thermostat element S may be so extended upon a stoppage of line current and consequent excessive rise in temperature in the box as to'possibly injure the thermostat element because of its low temperature setting. The spring 44 will ade-. quately provide for that. By way of illustrating the functioning of the pilot or cold control thermostat, the following example is given:If the low temperature contact 28 of circuit controller A is set at 31 F. with a minimum normal box temperature of 34 F. at the position of the pilot thermostat, the latter may be set at 32 F. which will prevent any low temperature dip in the box from actuating the defrosting device, and will assure the proper functioning thereof when circuit controller A contacts with the ice formation on the coils or baffles upon resumption of normal box temperature. This permits the use by the owner of the box of the cold control during the refrigerating cycle without any possibility that the defrosting cycle will start while the temperature of the box is thus lowered below normal. The device accordingly provides for starting the defrosting cycle at the proper time; will effect a complete removal of the ice formed on the coils and bai'lles, and will restore the refrigerating cycle following the elimination of the ice, with the minimum interval of time prevailing between such ice elimination and the resumption of the refrigerating cycle. Thus, the factor of owner's neglect or oversight will not serve to permit any undue formation of ice oh the cooling unit or permit the compressor to remain idle unduly long with a resulting abnormal rise in box temperature and consequent food spoilage.

While it has been proposed to use a rectified direct current of low voltage in connection with duced voltage current will be unnecessary. In

that event a solenoid of the type shown in Figure 9 may be used. This solenoid may be placed in the circuit including the wires 25a. and connected with a source of 110 volt alternating current. The solenoid is designated generally as 56 and includes the core portion 5| and the frame part 52. This frame is preferably directly connected with the plunger P which is adapted to alternately engage the heads of the dogs 0 and 0'. When alternating current is applied to the solenoid for an instant by the closing of the circuit through either of the contacts 26 and 21, the core 5i will be drawn to the center of the coil and when the current is cut off the core will be forced back to its outward position by the spring P2 ready for the next energization.

Referring again to the member B which projects into the cooling compartment of the ice box, it is pointed out that the same has a free pivotal mounting in the bracket I00 (see Fig. 4) This bracket is carried by the permanent or stationary base 6 and is secured thereto as indicated at IOI. The said bracket has an intermediate arm I02 and an upper arm I03, the former having a seat I64 for receiving the lower end of a bearing pin I65 whose upper end is adapted to be engaged by an adjusting screw I06. The bearing I05 is a part of the member B which has an angular pendant arm I01 which is provided with a collar I08 for receiving the tubular member B. While any suitable-and convenient means may be utilized for holding the tubular member B in the collar I08, a set screw I09 is preferable since it permits of accurate adjustment of the arm B. This type of bearing or support for the arm B which carries the ice contacting and following member A is of particular importance since it provides a substantially frictionless mounting for the arm B and enables the member A to freely and fully follow the ice formation and also requires a minimum amount of energy from the actuating parts to cause it to follow the ice and reset it to its initial position.

It will be readily appreciated that the members A and F are motor control switches, since they function to control the opening and closing of the circuit to the motor which is a part of the means for circulating the refrigerant medium through the evaporator. The motor control switch A is located at the evaporator and motor control switch F is mounted on the refrigerator housing, and, through the medium of the means of the elements I2. I3, and 20, can be manually adjusted to vary their efiective operation and in turn vary the temperature at the evaporator. Thus control of the refrigerator motor is conveniently provided for by the location on the refrigerator housing of a manually adjustable unit control knob and calibrated indicating temperatm-elimits, -of'a switchmechanismar ranged between the outerand inner walls, a

'member projecting said opening andoperatively to said m,

sealing means for closing the opening, and means I means to'establish temperature so of the temperature control means of the refrigerating apparatus. 1

In connection with the liquid seal device arranged at the opening A- it is pointed out that the same is preferably filled, with glycerine be-' cause of its non-volatile and hygroscopic proper ties. 'That is to say, glycerine will not be substantially affected by temperature conditions of the box and at the same timewill 1m indefinitely because it will not evaporate, has no odor and at V the same time tends to absorb moisture.

I claim:

i. In an apparatusfor automatically defrostingirefrigerating units the combination with a switch, for automatically opening and closing the circuit to the refrigerator motor, an ice following and contacting member, a thermostatically operated' circuit closercarried 'by'said ice contacting and jfollowing member and having low and high temperature contacts, and a thermostat operating ata temperature above or below the set temperature of said low contact and included in an 2. In an apparatus for automatically defrost-- ing refrigerating units, an ice contacting and following member, high and low temperature contacts carried by said member, a thermostatically controlled arm adapted to engage with said high and low temperature contacts, circuits for said a high and low temperature contacts and said arm, I and a thermostatic circuit closer included in the circuit of the low temperature. contact.

3. In an apparatus for automatically defrosting refrigerating units, an ice contacting and following member, high and low temperature contacts carried by. said member, a thermostatically controlled arm adapted to engage with said high and low temperature contacts, circuits for said high and low temperature contacts and said am,

, and a thermostatic circuit closer included in the circuit of the low temperature contact to open said circuit at temperatures above or below the setting of the said. low temperature contact.

4. In an electrical refrigerator, the combination with outer and inner walls enclosing the cooling chamber, an ice forming unit within the cooling chamber, means for circulating a refrigerant in the unit and means for maintaining the unit within predetermined temperature limits, of a defrosting device including a controlling member projecting through the inner wall of the refrigerator and in proximity to said ice forming unit.

5. In an electrical refrigerator, the combination with outer and inner walls enclosing the cooling chamber and the ice forming unit supported in said chamber, means for circulating a refrigerant in the unit and means for maintaining the unit within predetermined temperature limits, of a switch mechanism arranged between said outer and inner walls, a member projecting through the said inner wall and operatively connected to said switch mechanism, and means carried by said member for controlling the operation,

- of the switch.

6. In an electrical refrigerator, the combination with the outer and inner walls enclosing the cooling chamber and the ice forming unit therein, said inner wall having an opening, means for circulating a refrigerant in the unit and means for the unit within predetermined ation of the carried by the lever chamber.

carried by said member for controlling theoper- 7. In an electrical refrigerator. the combi-' nation with inner walls for enclosing'thecooling chamber, said inner wall having an ice forming unitsupported in.

said chamber, means for circulating 'a refrigerant in the unit, andmeans for maintaining the unit within predetermined temperature limits, of a mechanism, a liquid seal device for closing :the opening, and means carried by saidcontrolling the operation of themember for switch.

8. In an electrical refrigerator, the

tion -with outer and inner walls enclosing, the cooling chamber, said inner wall having an open-' v ing, an ice formingunit supported in the cooling chamber, means for circulating a refrigerant l in the unit and means for maintaining thevunit within predetermined temperature limits, of a Y 9. In an electrical refrigerator, the combina-' tion with outer and inner walls enclosing the cooling chamber, said inner wall having anopen ing, an ice forming unit for cooling said chant-- ber, means for circulating a refrigerant in the unit andmeans for maintaining the unit with in predetermined temperature limits, of, a defrosting device arranged between said outer and carried by the movable member and disposed in spaced relation to the refrigerating unit, and means for controlling the operation of said member, said means including a rod projecting through the outer and inner walls of the box and having a knob on the end thereof exposed on the outside of the box for manual manipulation to change the relative spacing of the thermostatic switch device with reference tothe refrigerating unit. 7 1 I 10. In an electrical refrigerator, the combi nation with outer and inner walls enclosing the cooling chamber, said inner wall having an open? ing, an ice forming unit for cooling said chamber, means for circulating a refrigerant in the unit and means 1o:- maintaining the unit within predetermined temperature limits, ofa tie frosting device arranged between said outer and Y innerwalls including a switch, switch throwing means, levers operated simultaneously with said g switch throwing means and certain of said levers 1 I extending through said opening into the cofol-f :in'g chamber, and a thermostatic circuit closer in circuit with said switch throwing means and '11. In an electrical refrigerator, the conibi-i projecting into the cooling Q inner walls and including a movable member projecting through said opening into the cool-1 v ing compartment, a thermostatic switch device nation with outer and inner walls enclosing the cooling chamber, said inner wall having an opening, an ice forming unit for cooling said chamber, means for circulating a refrigerant in the unit and means for maintaining the unit within predetermined temperature limits, of a defrosting device arranged between said outer and inner walls and including a switch for automatically opening and closing the circuit to the means for maintaining the ice forming unit within predetermined temperature limits, a control arm projecting through said opening into the cooling chamber, an ice contacting and following member carried by said arm, electrically operated actuating means for said switch and control arm, a circuit closer carried by said ice contacting and followingmember and electrically connected with said actuating means, and means exposed at the outside of the refrigerator for manually setting the ice contacting and following member in spaced relation to the ice forming unit.

12. In an electrical refrigerator, the combination with outer and inner walls enclosing a cooling chamber, one of said inner walls having an opening, an evaporator for the cooling chamber, means for circulating a refrigerant through the evaporator and means for maintaining the evaporator within predetermined temperature limits, of a defrosting device arranged between an outer and inner wall including a switch in circuit with the means for maintaining the evaporator within predetermined temperature limits, a control arm projecting through said opening in one of said inner walls, an ice contacting and following member carried by said arm, electrically operated actuating means for said control arm, a circuit closer carried by said ice contacting and following member and electrically connected with said actuating means, and means extending through another outer and inner wall and having a knob arranged in an exposed position on said latter outer wall for manual manipulation, and an indicating dial on said last mentioned outer wall cooperating with said knob for selectively setting the ice contacting and following member in spaced relation to the evaporator.

13. In an electrical refrigerator, the combination with outer and inner walls respectively enclosing the cooling chamber and means for maintaining a refrigerating cycle including an evaporator, means for circulating a refrigerant therein and means for maintaining the evaporator within predetermined temperature limits, of a defrosting device arranged between said outer and inner walls and including a reciprocating switch arm, motor circuit contacts and indicating circuit contacts arranged at the respective limits of movement of the reciprocating switch arm, a control arm projecting into the cooling chamber through one of said inner walls, an ice contacting and following member carried by said arm, electrically operated actuating means for said switch and control arm, a circuit closer carried by said ice contacting and following member and electrically connected with said actuating means, means extending through one of said outer walls for manually setting theice contacting and following member, means cooperating with said last named means for timing the refrigerating cycle, and means also arranged on one of said outer walls of the refrigerator and electrically connected with said indicating circuit contacts for indicating the performance or non-performance'of the refrigerating cycle.

14. In an electrical refrigerator, the combination with outer and inner walls enclosing the cooling chamber and means for maintaining a refrigerating cycle including an evaporator, means for circulating refrigerant therein and means for maintaining the evaporator within predetermined temperature limits, of a defrosting device arranged between certain of said outer and inner walls and including a switch connectedwith said means for maintaining the evaporator within predetermined temperature limits, a control arm projecting through an inner wall into the cooling chamber, a bracket supported at the inner side of said inner wall, a bearing mounted in said bracket, a member pivoted coaxially with said switch and operatively connected with said bearing, electrically operated actuating means for said switch and said member, an ice contacting and following member carried by said control arm, and a circuit closer carried by said ice contacting and following member and electrically connected with said actuating means.

15. In an electrical refrigerator, the combination of a housing having a cooling compartment, a door for said cooling compartment; refrigerating apparatus concealed within the housing and including an evaporator, means for circulating a refrigerant therein, means for maintaining the evaporator within predetermined temperature limits; means controlled by the formation and melting of ice on the evaporator for modifying the operation of said means for circulating refrigerant in the evaporator to effect defrosting, and means on an outer wall of the housing for indicating the initiation, duration, and termination of the period of defrosting.

l6.\In an electrical refrigerator, the combination of a housing having a cooling compartment, a door for said cooling compartment; refrigerating apparatus concealed within the housing and including an evaporator, means for circulating a refrigerant therein, means for maintaining the evaporator within predeterminedadapted to be selectively positioned to set the said means controlled by the formation and melting of ice to determine the period in which defrosting will not be effected; means also on an outer wall of the housing for indicating the initiation, duration, and termination of the period of defrosting.

17. In an electrical refrigerator, the combination of a housing having a cooling compartment, a door for said cooling compartment; refrigerating apparatus within the housing'an'd including an evaporator, means for circulating a refrigerant, therein, means for maintaining the,

evaporator within predetermined temperature limits; a' thermally controlled defrosting device for modifying the operation of said means-for circulating refrigerant in the evaporator to defrost the evaporator; and a ,device adapted to be selectively positioned to set the said defrosting device to determine the period in which defrosting will not be eflected.

18. In an electrical refrigerator, the combi-.

nation of a housing having a cooling compartment, 9, door for said cooling compartment; refrigerating apparatus within the housing and incan eluding an evaporator, means for circulating a refrigerant therein, means for maintaining the evaporator within predetermined .temperature limits; a thermally controlled defrosting device for modifying the operation of said means for circulating refrigerant in the evaporator for a period to defrost the evaporator; and means on an outer wall of the housing operativelv connected with said defrosting device for indicating the initiation, duration, and termination of the defrosting period.

19. In an electrical refrigerator, the combination with the evaporator, means for circulating a refrigerant in the evaporator, andmeans for maintaining the evaporator within predetermined temperature limits, of a thermally controlled de-.

frosting device adapted to be actuated at predetermined limits of temperature to modify the operation of said means for circulating refrigerant in the evaporator to defrost the evaporator,

' and means to'prevent effective operation of the defrosting device at a predetermined tempera-, ture condition of said device.

20. In an electrical refrigerator, the combination with the evaporator, means for circulating a refrigerant throughthe evaporator, means for maintaining the evaporator within predetermined temperature limits, means for'modifying'theoperation of said last named means to provide for selectively maintaining a lower temperature at the evaporator, and a defrosting device to defrost the evaporator, of means to prevent the, efiective operation of said defrosting device upon actuation of said means for selectively maintaining a lower'temperature at the evaporator.

21. In an electrical refrigerator, the combination with the-evaporator; means for circulating a refrigerant in the evaporator, means for main-v taining the evaporator within predetermined, temperature 'limits,'means for modifying the -operation of said last named means to obtain increased cold conditions 'atthe evaporator; of

means for automatically defrosting the evaporator, including a device for rendering inoperative said means for automatically defrosting the evaporator while the means for modifyingthe operation of said second named means is in operation. 7

22. In an electrical refrigerator, the combination with the evaporator, means for circulating a refrigerant through the evaporator, means for maintaining the evaporator within predetermined temperature limits, and means for modifying the operation of said last named means to provide for selectively maintaining a lower temperature at the evaporator; of a defrosting device to defrost the evaporator, said device being controlled by the formation and melting of ,ice on the evaporator.

23, In an electrical refrigerator, the combination with the evaporator and motor concealed within the refrigerator housing, means for circulating a refrigerant in the evaporator, means for maintaining the evaporator within predetermined variable temperature limits, and a current supply line for furnishing current to said two last named means; of a member for opening the circuit in said current supply line for a period to defrost the evaporator and for closing the circuit at the end of said period, automatic means for actuating said member to initiate and terminatethe defrosting period, and means on an outer wall of said housing for indicating the initiation, duration, and termination of the defrosting period.

24. In an electrical refrigerator including a housing having an exterior panel,'the combination with the evaporator, means for circulating a refrigerant in the evaporator, means for maintaining the evaporator within predetermined variable' temperature limits, and a current supply line for furnishing current to said two last named means, of a member including means for automatically opening the circuit in said current supply line for a period to defrost the evaporator and for closing the circuit at the end of said period, means located on said panel for selectively positioning said member to determine the period in which defrosting .will not be effected; and

means operatively connected with said member for indicating the initiation, duration, and termination of the defrosting period.

25. In combination, a refrigerator cabinet having an interior cooling chamber and anexterior panel, an evaporator in the cooling chamber, means for circulatingv a refrigerant through the evaporator, means for maintaining the evaporator within predetermined temperature limits, means for defrosting the evaporator, means arranged on said panel adapted to be positioned to selectively choose the period of the refrigerating cycle and prevent'the operation of said means for defrosting .until predetermined frost conditions occur on the evaporator, and means also on said panel, for indicating the initiation, duration, and

termination of the defrosting period.

26. In combination, a refrigerator cabinet hav ing an interior cooling chamber and an exterior panel, an evaporator in the cooling chamber,

'means'for circulating" a r'efrigerant'through the evaporator, means for maintaining the evaporator within predetermined temperature limits, I

means for defrosting the evaporator, and means, arranged on said panel adapted to be positioned to selectively choose the period of the refrigerating cycle and-prevent the operation of said means for defrosting until predetermined frost conditions occur on the evaporator. v v 27. In an electrical refrigerator, the combination of a housing having a cooling compartment,

refrigerating apparatus within the housing and 3 including anevaporator in the cooling compart ment, means for circulating a refrigerant medium through the evaporator including a motor, switch mechanism .for controlling the 'motorlocated within the walls of the housing and including a thermal cutout in operative proximity to the evaporator, an adjustment control for the switch mechanism, a unit control" including a knob rotatable to operate the adjustment control and extending'outside the housing; and means actuated bythe knob at opposite positionsof its movement, to render the thermal cutout effective and ineflective respectively. v

28. In an electrical refrigerator, the combination of a housing having a cooling compartment, refrigerating'apparatus within the housing and including an evaporator in the cooling comparte ment, means for circulating a refrigerant medium through the evaporator including a motor,

a plurality' of motor control switches, .anadiustment control for one of said switches, and a unit control comprising means for actuating the adjustment control to change its effective position, said means including a rotatable part located on the housingand being ,operatively the last mentioned switch. I I 29. In an electrical refrigerator, the combination of a housing having a coolingoompartment,

refrigerating. apparatus within the housing and associated with effect of said control means to maintain the evapincluding an evaporator in the cooling compartment, means for circulating a refrigerant medium through the evaporator including a motor, temperature responsive motor control structure having a thermal cutout device and an adjustment control device, a unit control comprising means for actuating the adjustment control, said means including a rotatable knob located on said housing and being operatively associated with said thermal cutout device to provide a plurality of predetermined temperature settings of said thermal cutout.

30. A refrigerating system, comprising in combination a cooling element normally maintained at desired refrigerating temperatures, means rendered operable automatically at intervals by the normal operation of the system to permit rise of the temperature of the cooling element to a defrosting temperature limit, and means for varying the refrigerating temperatures while maintaining the upper limit of defrosting temperature of the cooling element constant regardless of variation of the normal refrigerating temperature.

31. In a refrigerating apparatus, means for producing a plurality of cycles of operation, comprising means for limiting the operations of the apparatus between normal refrigerating temperature limits for a plurality of periods and means for maintaining the apparatus between the defrosting temperature limit and the low normal temperature limit for a plurality of periods, each of said normal refrigerating temperature periods followed by a defrosting period and means for varying the normal refrigerating temperature limits while maintaining the high defrosting temperature limit constant.

32. Refrigerating apparatus including an evaporator, means for circulating a refrigerant through the evaporator, automatically operating means associated with, and responsive to a condition of refrigerating apparatus for automatically-at intervals effecting defrosting of the evaporator, and means for varying the frequency of the defrosting operation.

33. Refrigerating apparatus including an evaporator and means for circulating a refrigerant through the evaporator, a control means for maintaining the evaporator within certain temperature limits, manual means movable to a plurality of selected positions for varying the orator between other selected temperature limits, and automatic means for initiating and terminating defrosting of the evaporator. g

34. Refrigerating apparatus including an evaporator and means for circulating a refrigerant through the evaporator, means for controlling said circulating means to maintain an average temperature in the evaporator, a readily accessible manual means movable at will by the user to a plurality of selected positions to vary the effect of the control means whereby a plurality of different selected average temperatures may be maintained in the evaporator, and means for automatically defrosting the evaporator.

35. A refrigerating system including an evaporator and means for circulating a refrigerant through the! evaporator, means for controlling said circulating means, said last named means having a customer adjustment movable to a plurality of selected positions for varying the effect of the control means, and means for automatically defrosting the evaporator.

36. A refrigerating system including an evaporator and means for circulating a refrigerant through the evaporator, a control means for said circulating means to maintain an average temperature in the evaporator, said last named means havinga customer adjustment movable to a plurality of selected positions to vary the effect of the control means to thereby obtain a plurality of different selected average temperatures in the evaporator, means for automatically defrosting the evaporator, and means for preventing the operation of said defrosting means when the customer adjustment has been moved to one of its selected positions.

37. A refrigerating apparatus including an evaporator and means for circulating a refriger:

ating medium through the evaporator, means for controlling said circulating means, and means for automatically defrosting the evaporator and means associated with said refrigerating system for indicating that the defrosting means is in operation.

38. A control for refrigerators, including means for normally maintaining operating cycles between fixed temperature limits, means for adjusting the temperature limits of said operating cycles, means for producing a higher temperature limit for a defrosting cycle, one of said means including means whereby the higher temperature limit of the defrosting cycle remains substantially constant regardless of the adjustment of the temperature limits of the normal operating cycles.

39. In a control for refrigerators, means for normally maintaining operating cycles between fixed temperature limits, means for varying the temperature limits of said normally operating cycles, means for modifying the upper temperature limit of the normal operating cycles to produce a defrosting cycle, means for automatically terminating the defrosting cycle, means whereby the upper temperature limit of the defrosting cycle remains at a practically fixed value regardless of the adjustment of the temperature limits of the normal operating cycles upon the completion of the defrosting cycle.

40. A control for refrigerators including means for normally maintaining operating cycles between fixed temperature limits, means for adjusting the temperature limits of said operating cycles, means rendered operable automatically at intervals by the normal operation of the system for producing a higher temperature limit for a defrosting cycle, one of said means including means whereby the higher temperature limit of I the defrosting cycle remains substantially constant regardless of the adjustment of the temperature limits of the normal operating cycles.

41. In a refrigerating apparatus, the combination of controlling means for limiting the operations of the apparatus to produce a refrigerating temperature between certain normal temperature limits, means for adjusting the normal temperature limits, means for altering one of the normal temperature limits to produce a predetermined temperature point materially removed from said normal temperature limits, one of said means in-- cluding means for maintaining the said materially removed predetermined temperature point substantially constant regardless of the adjustment of the normal refrigerating temperature limits.

42. A refrigerating system comprising in combination,-a cooling element normally maintained between desired upper and lower temperature limits, means operating automatically at intervals for raising the upper temperature limit oi the cooling element to a' tially constant defrosting temperature.

43. A refrigerating system comprising in combination, a cooling element, means for normally maintaining the cooling element between desired upper and lower normal temperature limits, means for adjusting one of said temperature limits, and an independent means for changing one of said temperature limits to an abnormal predetermined substantially fixed temperature limit, regardless of the adjustment of said desired upper and lower normal temperature limits.

44. A refrigerating system comprising in combination, a cooling element, means for normally maintaining the cooling element between desired upper and lower normal temperature limits,

vmeans for adjusting one of said temperature limits, and an independent means for changing one of said temperature limits to a predetermined substantially fixed abnormal temperature limit, regardless of the adjustment of one of said desired upper and lower normal temperature limits,

I 9 said last named means including means for returning the cooling element to the adjusted upper and lower temperature limits upon the reaching of said substantially fixed abnormal temperature limit. 7

45. A refrigerating system comprising in combination, a cooling element, means for normally maintaining the cooling element between desired upper and lower normal temperature limits,

means for adjusting one of said temperature 10 limits, and an independent means for changing one of said temperature limits to a predetermined substantially fixed abnormal temperature limit, regardless of the adjustment of one of said desired upper and lower normal temperature limits. 15

46. Refrigerating apparatus including an evaporator, means for circulating a refrigerant medium through the evaporator, automatically operateii means associated with the refrigerating apparatus for automatically at intervals effect- '20 ing defrosting of the evaporator, and means for varying the'frequency of the defrosting operation.

CHARIES T. HOFFMAN. 

